Flag docker invocations as --privileged on CI

When upgrading to LLVM 5.0 it was found that the leak sanitizer tests were
failing with fatal errors, but they were passing locally when run. Turns out it
looks like they may be using new ptrace-like syscalls so the docker container
now needs `--privileged` when executing to complete the test.

src/ci/docker/run.sh

@@ -67,6 +67,13 @@ else
     args="$args --env SCCACHE_DIR=/sccache --volume $HOME/.cache/sccache:/sccache"
 fi
 
+# Run containers as privileged as it should give them access to some more
+# syscalls such as ptrace and whatnot. In the upgrade to LLVM 5.0 it was
+# discovered that the leak sanitizer apparently needs these syscalls nowadays so
+# we'll need `--privileged` for at least the `x86_64-gnu` builder, so this just
+# goes ahead and sets it for all builders.
+args="$args --privileged"
+
 exec docker \
   run \
   --volume "$root_dir:/checkout:ro" \